Controlling nitrogen oxide (“NOx”) emissions in internal combustion engines has posed significant challenges to the automotive industry. One method for controlling NOx emissions is generally known as exhaust gas recirculation (EGR). This method utilizes a conduit to recirculate exhaust gases into the engine intake. The recirculated exhaust gases absorb heat in the combustion chamber, thereby lowering the temperatures within the combustion chamber and lowering the production of NOx. A cooler may be provided along the EGR conduit to cool the recirculated exhaust gases and thereby help further lower combustion temperatures.
In a turbocharged engine, two types of EGR systems may be employed. The first may be referred to as a high pressure EGR system, and recirculates exhaust from a location upstream of the exhaust turbine. The second may be referred to as a low pressure EGR system, and recirculates exhaust from a location downstream of the exhaust turbine.
A low pressure EGR system may recirculate exhaust gases to the engine intake at a location either upstream or downstream of the intake compressor. In a low pressure EGR system where recirculated exhaust is delivered to the intake upstream of a compressor, particulate matter in the recirculated exhaust can damage the compressor. To help prevent such damage, the low pressure EGR system may draw exhaust from a location downstream of a particulate filter such that particulate matter is removed from the exhaust before it reaches the low pressure EGR intake. However, failure of the particulate filter may occur, in which case particulate matter in the exhaust may damage the intake compressor, EGR cooler, charge air cooler, and/or other engine components.
The inventors herein have realized that particulate damage to an engine may be avoided or lessened in an apparatus having an internal combustion engine, a compressor for compressing engine intake gases, a particulate filter for filtering particulate matter from engine exhaust, an exhaust gas recirculation (EGR) system for recirculating exhaust gases from a location downstream of the particulate filter to a location upstream of the compressor, and a particulate filter function detector configured to detect a failure of particulate filter, by performing a method of operating the engine including receiving a signal from the particulate filter function detector, comparing the signal from the particulate filter function detector to a predetermined signal threshold, determining if the signal received from the particulate filter function detector meets a predetermined condition relative to the predetermined signal threshold; and reducing a flow of exhaust gas through the EGR system if the signal meets the predetermined condition.